This invention relates to the enhancement of the durability of emollient materials with certain organosilicon compounds. More particularly, the durability of mineral oil, for example, on human skin is enhanced by mixing the emollient with one of aminofunctional, amidofunctional, or carboxyfunctional, polysiloxanes.
Mineral oil is a highly refined, colorless, tasteless, and odorless, liquid mixture of hydrocarbons obtained from petroleum, that has been used medicinally as an internal lubricant and in the manufacture of various salves and ointments. It is also known as medicinal oil, white mineral oil, heavy mineral oil, light mineral oil, liquid paraffin, and paraffin oil. Mineral oil has long been the emollient of choice in creams and lotions. It is second only to water as a moisturizer ingredient. Mineral oil acts as a moisturizer primarily through the functioning of the ingredient as an occlusive barrier. The water content of the outer layers of the stratum corneum of the human skin is a controlling factor in the appearance of dry skin symptoms. When the stratum corneum contains an adequate amount of water within the range of ten to twenty percent, the skin remains flexible. However, when the water content falls below ten percent, the stratum corneum often becomes brittle and rough, and can exhibit scaling and cracking.
The stratum corneum receives its water from the deep layers of the epidermis by diffusion or when it is brought into direct contact with water. The diffusion process is controlled by the water content of the skin, as well as the concentration gradient. In a very dry environment, the water loss from the external skin layers can be significant and often exceeds the rate of replacement by diffusion. An occlusive barrier of mineral oil, for example, placed onto the surface of the skin acts to retard the water loss to the environment and allows the skin surface to rehydrate by the diffusion process. Due to the effectiveness, low cost, and safety, of petroleum derivatives such as mineral oil, it serves as a useful occlusive moisturizer and contributes to dry skin prevention by protection and moisture retention, as well as dry skin repair by emolliency, lubricity, and moisture restoration.
While mineral oil has been found to be an effective and economical emollient for skin care applications, and provides softening, smoothing, and a protective action on skin, it nevertheless suffers from the disadvantage that it is easily removed from the skin by washing the skin with soap. Thus, the effectiveness and long term benefits of mineral oil enumerated above are of a limited duration. However, in accordance with the present invention, it has been discovered that certain aminofunctional, amidofunctional, and carboxyfunctional, organosilicon compounds act as durability enhancers when mixed with mineral oil, and therefore provide skin care formulations that a consumer can perceive as being longer lasting and more aesthetically pleasing.
It is not new, as noted above, to employ mineral oil in skin conditioning formulations. For example, this feature is clearly taught, for example, in U.S. Pat. No. 3,818,105, issued June 18, 1974, and in U.S. Pat. No. 4,246,285, issued Jan. 20, 1981. Aminofunctional, amidofunctional, and carboxyfunctional, organosilicon compounds are also not new, and certain of such siloxanes are shown, for example, in U.S. Pat. No. 4,271,215, issued June 2, 1981; U.S. Pat. No. 4,477,514, issued Oct. 16, 1984; U.S. Pat. No. 4,559,227, issued Dec. 17, 1985; U.S. Pat. No. 4,563,347, issued Jan. 7, 1986; U.S. Pat. No. 4,749,732, issued June 7, 1988; U.S. Pat. No. 4,810,253, issued Mar. 7, 1989; U.S. Pat. No. 4,848,981, issued July 18, 1989; and in U.S. Pat. No. 4,857,212, issued Aug. 15, 1989. However, none of these references teach the combination of mineral oil with such siloxanes and there use on the skin as durability enhancers. Formulations containing mineral oil and an aminofunctional siloxane are know as exemplified by U.S. Pat. No. 3,852,075, issued Dec. 3, 1974, and U.S. Pat. No. 4,113,677, issued Sept. 12, 1978, but such formulations are employed to clean and polish automotive vehicles rather than as personal skin care applications.